PARIS - Two mysteries that have long puzzled students of libational history and worldly business travelers are "how many of the many Harry's Bars around the world are authentic?" and "what was Ernest Hemingway's favorite cocktail?" Although hardly as vexing as "The DaVinci Code," the answers are here in Paris and the hunt for truth can be a delicious and unforgettable adventure.

While Harry's Bar in Venice, Italy - a rude, overpriced tourist trap - has long passed itself off as the original, Harry's New York Bar on 5 Rue Daunou in Paris ( www.harrys-bar.fr; 011331-4261-7114) holds that distinction - and many others. It claims to be the oldest cocktail bar in Europe (I can't prove it) but this much is fact: An American jockey named Tod Sloan convinced a New York saloon owner named Clancey to dismantle his barroom, ship it to Paris and open the New York Bar in Paris on this very location where a bistro once stood. Sloan recruited Harry MacElhone, a Scot from Dundee with a hot rep as a great bartender, to work the plank, and opened on Thanksgiving Day in 1911.

The bar was a smashing success and became a hangout for the racing crowd and, later, wartime ambulance drivers. Harry MacElhone went home a year later to tend bar at the Plaza Hotel, returned to Paris in 1923 at the dawn of the Roaring '20s, bought the bar and put his name on the door.

The rest is verifiable history. George Gershwin composed much of his "American in Paris" at the piano in the Downstairs Room. An often-morose F. Scott Fitzgerald sucked down dry martinis with other budding American literati who dubbed themselves the Lost Generation. Hemingway, by then a freelance magazine journalist after covering World War I for the Kansas City Star, blustered into Harry's after amateur boxing bouts to gloat or lick his wounds.

In 1924, Harry and a raconteur named O.O. McIntyre formed the International Bar Flies celebrating the joys of serious cocktailing; today, there are roughly 134 chapters worldwide known as "Fly Traps" and membership stands at 50 euros or U.S. $63. Membership benefits? Camaraderie.

My first visit to Harry's New York Bar in the late '70s is seared in my memory. It was almost empty on a Saturday afternoon except for a delightful couple in their early 80s - an Irish poet and 'girlfriend' of 45 years - who regaled me with the history of Harry's Bar. "Yes, I remember drinking with Hem," said the poet, his deep blue eyes still twinkling. "He drank gin or bloody marys. Couldn't hold his liquor. He'd get mean."

I've heard that before. But then Harry's, a cozy, woodsy storefront saloon that glows in that Paris bistro sort of way, was a welcoming haunt then for expats and the curious and it remains so today. English is spoken fluently, the American hot dog is star of the menu, and jazz piano is still live downstairs. In a recent conversation, Alan Da Silva, who manages Harry's for the heirs of the original owners, insists a mixologist named Pete Pekeot invented the bloody mary right here 85 years ago; it is now made with Wyrosova Polish vodka and fetches U.S. $15 at the current Euro exchange rate. Harry's is also the birthplace of other classic cocktails including the French 75, sidecar and white lady. Also popular (and tasty) is the blue lagoon for two: vodka, grapefruit juice and blue Curacao served tall for U.S. $15.

Harry's isn't a slave to the past with inventive drinks such as the Web spirit, crafted in honor of its Internet site: mezcal, cranberry juice, lemon juice and peach liquor. Meantime, don't try to take home any souvenirs from Hemmingway's days. Staffers are on permanent high alert ever since someone walked off with a bar stool engraved with Hemingway's name, a gift from Harry.

Instead, give yourself an unforgettable gift - a drink handmade by Colin Field, head barman at the Bar Hemingway in the Ritz Hotel in Paris ( www.ritzparis.com; 011-33-1-4316-3365). The bar, which feels more like an exquisite drawing room in a private home, is tastefully festooned with historic photographs, sculptures, and fine crystal. It's been hailed, by regulars, not press agents, as the finest bar in the world - and it has the drinks and barman to match. Field won the Martini Grand Prix in 2001 and can rightfully be termed, without exaggeration, the world's best barman.

The Englishman is witty, as smooth as 50-year-old cognac, a great storyteller, and the perfect host who often introduces total strangers - and entire tables of guests - to one another.

His signature Picasso martini is made with Tanquerey, which he deems the best of all English-style gins, and a small frozen cube of Noilly Pratt vermouth. "Picasso, cubism, you get the idea," he says dryly.

The genius of a great barman is the subtle, simple marriage of tastes and flavors. Field proves his prowess with his Ritz cider, a blend of apple juice and Champagne or Kashenka, a mating of Polish vodka and strawberries. You'll pay dearly for these - 26 Euros, or $33 at the current exchange rate - but when amortized over a lifetime of memories, the price of this rare experience is soon forgotten.

Never to be forgotten, though, is Hemingway's army of rascals and revelers who rolled back into Paris on Aug. 25, 1944, when the Axis powers surrendered to the Allies, and "liberated" the Ritz Hotel from German rule by swigging champagne in the Little Bar that now fittingly bears his name. They liberated other bars that day and were said to be pretty toasted by the time they stormed the Ritz. Thus, the answer to the burning question of the literary lion's libation of choice: he had no favorite, his taste buds were democratic. From dry gin martinis, bloody marys, Champagne to beer, daiquiris, mojitos to the "milky green fairy" known as absinthe. Just don't order one from Colin Field; absinthe is still outlawed worldwide.

Chris Barnett writes on business travel strategies that save time, money and hassles.